The present invention relates to a magneto-optic recording/reproducing method and device and a magneto-optic recording medium used for them. More particularly, the present invention relates to a magneto-optic recording/reproducing method which is suitable to accurately demodulate data at a high speed by suppressing jitter due to "feather-shaped magnetic domains" which will be generated in performing overwrite through magnetic field modulation.
A magneto-optic disk has been identified as an optic disk which can rewrite information. The magneto-optic disk, using a vertically magnetized film as a recording film, forms recording domains through a thermomagnetic effect and reproduces them through a magneto-optic effect. More specifically, the recording domains are formed as follows. The temperature of the magnetized film is increased to its Curie temperature by irradiating a laser optical spot to remove the magnetization of the irradiated area, and in the cooling process an external magnetic field is applied to fix the vertical magnetization of the optical spot irradiated area in the direction of the magnetic field, thereby forming the recording (magnetized) domains.
The method for forming such magnetized domains includes two techniques. One is an optical modulation technique which, with an external magnetic field with a certain intensity applied in the direction opposite to the direction of initial magnetization of the vertically magnetized film, modulates the intensity of the laser optical spot in accordance with the data to be recorded. The other is a magnetic field modulation technique which, with the laser optical spot with a certain intensity applied to increase the temperature of the magnetized film to its Curie temperature or more, modulates the direction of the external magnetic field. For example, the technical Report at the Academic Society of Electronics, Information and Communication (DENSI JOHO TSUSIN GAKKAI GIJUTSU HOKOKU) MR 87-37 (1987), pages 13 to 20, discloses that a storage density of 0.6 .mu.m/bit is obtained at a scanning speed (linear velocity) of a laser light beam of 1.2 m/sec. through the magnetic field modulation technique.
However, this reference does not refer to the influence from the angular projections of the recorded magnetized domains and the change of the center position and width of the magnetized domains, and also does not entirely consider problems in the case of overwrite and reproduction at a high speed and with a high density.